Field of the Invention
The disclosure relates generally to power converters, and more particularly it relates to methods and circuits for adaptively controlling active-clamp flyback power converters.
Description of the Related Art
Since the functions of the electronic products are increased, a power supply is needed to provide more output energy. At the same time, consumers demand smaller electronic products, with a smaller volume and lighter weight. These trends form two requirements regarding power converters: raising the power density and improving conversion efficiency. Based on these two requirements, a large amount of active-clamp flyback converters and their derivative circuits are being applied to various power supply products due to their advantages, which include recycling the transformer leakage energy while minimizing turn-off voltage stress and having a soft-switching function for the power switch. For the conventional active-clamp flyback converters, the control scheme can only use complementary control mode or non-complementary control mode. Since these two control schemes cannot be selectively adopted in one converter, it is difficult to optimize the efficiency curve over a wide load range for universal ac input applications.